Torque estimation method for an internal combustion engine

Abstract

A method is presented for correcting estimates of engine output torque and accessory load torque. Engine output torque estimates are corrected when the accessory is disengaged from the engine. Accessory load torque is learned, or corrected, when the accessory is engaged to the engine. In one example, these corrections are made when engine output torque is known to be substantially zero from torque converter speed ratio or from the timing of the overrunning clutch engagement. This information is then used to control engine output torque to improve drive feel and vehicle performance.

I claim:  
     
       1. A method for use with an internal combustion engine in a powertrain coupled to a device having an input speed and an output speed, comprising: 
       indicating that powertrain output torque is less than a predetermined value based on the input speed and the output speed of the device; and  
       learning a powertrain torque adjustment value in response to said indication.  
     
     
       2. The method recited in  claim 1  wherein said powertrain torque is an engine torque. 
     
     
       3. The method recited in  claim 1  wherein the device is a torque converter. 
     
     
       4. The method recited in  claim 1  wherein the device is a transmission with an overrunning clutch. 
     
     
       5. The method recited in  claim 1  wherein said indicating is done when transmission output speed becomes greater than transmission input speed. 
     
     
       6. The method recited in  claim 3  wherein said indicating is done when output speed of torque converter becomes approximately equal to input speed of torque converter. 
     
     
       7. The method recited in  claim 5  further comprising indicating when a ratio of output speed to input speed becomes greater than said gear ratio of the transmission. 
     
     
       8. A powertrain torque estimation method for use with an internal combustion engine in a powertrain coupled to a device having an input speed and an output speed, comprising: 
       indicating that powertrain output torque is less than a predetermined value based on the input speed and the output speed of the device,  
       learning a powertrain torque adjustment value in response to said indication,  
       calculating actual powertrain torque based on a powertrain operating condition and said powertrain adjustment value,  
       determining desired powertrain torque based on an operator input; and  
       controlling a powertrain parameter to reduce a difference between said actual powertrain torque and said desired powertrain torque.  
     
     
       9. The method recited in  claim 8  wherein said powertrain torque is an engine torque. 
     
     
       10. The method recited in  claim 8  wherein the device is a torque converter. 
     
     
       11. The method recited in  claim 8  wherein the device is a transmission with an overrunning clutch. 
     
     
       12. The method recited in  claim 8  wherein said indicating is done when transmission output speed becomes greater than transmission input speed. 
     
     
       13. The method recited in  claim 10  wherein said indicating is done when output speed of torque converter becomes approximately equal to input speed of torque converter. 
     
     
       14. The method recited in  claim 12  further comprising indicating when a ratio of output speed to input speed becomes greater than a gear ratio of the transmission. 
     
     
       15. The method recited in  claim 8  wherein said operator input is pedal position. 
     
     
       16. The method recited in  claim 8  wherein said powertrain operating condition is an engine operating condition. 
     
     
       17. The method recited in  claim 16  wherein said engine operating condition is manifold air pressure. 
     
     
       18. The method recited in  claim 16  wherein said powertrain parameter is throttle position. 
     
     
       19. The method recited in  claim 16  wherein said engine operating condition is air/fuel ratio. 
     
     
       20. The method recited in  claim 8  wherein said learning powertrain torque adjustment value further comprises learning a load torque of an accessory coupled to the engine. 
     
     
       21. The method recited in  claim 20  wherein said accessory is air conditioning compressor. 
     
     
       22. An article of manufacture comprising a computer storage medium having a computer program encoded therein for use with an internal combustion engine in a powertrain coupled to a device having an input speed and an output speed, said computer storage medium comprising: 
       code for indicating that powertrain output torque is less than a predetermined value based on the input speed and the output speed of the device;  
       code for learning a powertrain torque adjustment value in response to said indication;  
       code for calculating actual powertrain torque based on a powertrain operating condition and said powertrain adjustment value;  
       code for determining desired powertrain torque based on an operator input; and  
       code for controlling a powertrain parameter to reduce the difference between said actual powertrain torque and said desired powertrain torque.